Finisher for an image forming apparatus

Abstract

A finisher for finishing papers sequentially driven out of an image forming apparatus includes a plurality of trays selectively movable to a single paper outlet. The finisher reduces a period of time necessary for designated one of the trays to reach the paper outlet, increases the number of papers which can be stacked on the trays, and determines the number of papers stacked with a simple configuration. Papers are prevented from returning from the tray to the paper outlet without complicating the configuration of the outlet. An outlet roller protrudes from the paper outlet, but does not interfere with the tray moving past the paper outlet. The trays protect the operator from injury and protect the structural elements of the finisher from damage despite their movement.

What is claimed is:  
     
       1. A finisher for an image forming apparatus, comprising: 
       a paper outlet for discharging papers;  
       a plurality of trays capable of being selectively located at said paper outlet and including at least an upper tray and a lower tray movable up and down independently of each other; and  
       control means for locating a designated one of said upper tray and said lower tray at said paper outlet;  
       wherein a retracted position assigned to said upper tray is defined above said paper outlet, and wherein said upper tray is movable via said paper outlet and includes an end fence movable up and down in synchronism with a stacking surface of said upper tray for positioning edges of the papers.  
     
     
       2. A finisher as claimed in claim  1 , wherein said control means moves said upper tray away from said outlet in a direction of paper discharge when moving past said paper outlet. 
     
     
       3. A finisher as claimed in claim  1 , further comprising a discharge position sensor for locating either one of said upper tray and said lower tray at said paper outlet, said lower tray being movable to a retracted position defined below a paper discharge position defined by said discharge position sensor by a first preselected distance. 
     
     
       4. A finisher as claimed in claim  3 , wherein said control means moves said lower tray to a first preselected position that allows said upper tray to move to said paper discharge position and allows the papers to be removed from said lower tray. 
     
     
       5. A finisher as claimed in claim  4 , further comprising a lower limit position sensor responsive to a lower limit position of said lower tray and located to allow said lower tray having been sensed by said lower limit position sensor to move downward by a second preselected distance. 
     
     
       6. A finisher as claimed in claim  5 , wherein said second preselected distance is greater than said first preselected distance. 
     
     
       7. In a finisher including a plurality of trays for sequentially stacking papers driven out of an image forming apparatus and stapled or otherwise finished, at least one of said plurality of trays includes an end fence for positioning trailing edges of the papers and a stacking surface which are movable up and down in synchronism with each other, and another one of said plurality of trays has an end fence implemented by a wall of a body of said finisher. 
     
     
       8. A finisher as claimed in claim  7 , wherein said plurality of trays are movable up and down along shared guide rails. 
     
     
       9. A finisher as claimed in claim  7 , wherein said plurality of trays are moved independently of each other. 
     
     
       10. A finisher as claimed in claim  7 , wherein said another of said plurality of trays comprises a bottom tray movable up and down. 
     
     
       11. A finisher as claimed in claim  7 , further comprising control means for selecting and positioning said plurality of said trays, and wherein when any one of said plurality of trays is selected in accordance with a mode selected on said image forming apparatus, the tray selected is positioned at a paper discharge position independently of the other trays. 
     
     
       12. In a finisher including a plurality of trays for sequentially stacking papers driven out of an image forming apparatus and stapled or otherwise finished, at least one of said plurality of trays includes an end fence for positioning trailing edges of the papers and a stacking surface which are movable up and down in synchronism with each other, said plurality of trays are movable up and down along guide rails extending in an up-and-down direction, and said guide rails each include at least one bent portion from interfering with a discharge of the papers toward said tray. 
     
     
       13. In a finisher including a plurality of trays for sequentially stacking papers driven out of an image forming apparatus and stapled or otherwise finished, at least one of said plurality of trays includes an end fence for positioning trailing edges of the papers and a stacking surface which are movable up and down in synchronism with each other, said plurality of guide trays are supported by a plurality of guide means positioned at a pitch L 1  on said tray and engageable with guide rails extending in an up-and-down direction, and said guide rails each include at least one bent portion having a length L smaller than the pitch L 1  at which said guide means are arranged on said tray having said end fence and said stacking surface.